Abrasive finishing article

ABSTRACT

DISCLOSES AN ABRASIVE POLISHING OR FINISHING ARTICLE CONSISTING OF A BACKING LAYER MADE OF CHAMOIS LEATHER, OR EQUIVALENT, POROUS TO SLURRIES SUCH AS WATER OR OIL, AND COATED ON THE FRONT SURFACES WITH A MATRIX CONSISTING OF A THERMOPLASTIC, FLEXIBLE BINDER, IN WHICH ARE EMBEDDED ABRASIVE PARTICLES ORIENTATED IN LARGE PART WITH PLANE FACES THEREOF FACING UPWARDS TO ENGAGE THE SURFACE TO BE POLISHED. THE ABRASIVE INCORPORATING THERMOPLASTIC COATING IS PREFERABLY DISPOSED IN A PATTERN OF &#34;ISLANDS,&#34; SO AS TO LEAVE CHANNELS THEREBETWEEN FOR CIRCULATION OF SLURRY.

Sept. 20, 1971 F. B. ANTHON ABRASIVE FINISHING ARTICLE Filed May 8. 1969 O Z M United States Patent O 3,605,349 ABRASIVE FINISHING ARTICLE Frederick B. Anthon, Los Angeles, Calif. (R0. Box 1759, Beverly Hills, Calif. 90213) Filed May 8, 1969, Ser. No. 823,084 Int. Cl. B24d 11/02 US. Cl. 51-402 9 Claims ABSTRACT OF THE DISCLOSURE Discloses an abrasive polishing or finishing article consisting of a backing layer made of chamois leather, or equivalent, porous to slurries such as water or oil, and coated on the fornt surface with a matrix consisting of a thermoplastic, flexible binder, in which are embedded abrasive particles oriented in large part with plane faces thereof facing upwards to engage the surface to be polished. The abrasive incorporating thermoplastic coating is preferably disposed in a pattern of islands, so as to leave channels therebetween for circulation of slurry.

FIELD OF THE INVENTION This invention relates generally to abrasives, and more particularly to abrasive articles of the type comprising abrasive grit adhering to a backing of paper, cloth, or the like, The invention is further directed to a special class of such abrasive articles where the purpose is cleansing, or fine finishing of surfaces, rather than actual cutting or stock removal. The articles of the invention are thus directed to operate, without cutting or scratching, on the surfaces of glass, plastics, jewelry, anodized finishes on aluminum aircraft parts, fine paintings, etc., which would be ruined by the common abrasives, but which can be cleansed or polished by articles of the present class without marring or scratching such as can be detected by the human eye.

BACKGROUND OF THE INVENTION The closest prior art of which I am aware is my prior Pat. No. 3,230,672, wherein fine grit is incorporated in a layer of latex on a textile backing sheet, with the grits oriented insofar as is possible so that substantially plane faces or facets on the grits are in a common plane just above the surface of the latex binding layer. The grits are thus cushioned by this latex layer, and give or rock, or become depressed slightly, so that, it points or edges of individual grits should happen to engage the surface to be polished, they will give slightly, and avoid scratching or digging into the work surface to be finished. This prior product has proved to be a great improvement over abrasive papers or cloths having unoriented grits, and especially those that are supported rigidly, like plows. The general object of the present invention is to provide a still further improved abrasive article, constructed in a novel fashion so as to be used to advantage with a slurry of water or oil, which continuously carries away the removed material, and thus prevents the abrasive surface from loading up. A further purpose is to provide improved and deeper cushioning for the abrasive particles, to facilitate their depression to a nonscratching position in any cases in which the abrasive particles should have sharp peaks or edges rising to or beyond the plane of the work. A further purpose of the inven- 3,605,349 Patented Sept. 20, 1971 ice- SUMMARY OF THE INVENTION In its most highly preferred form, the backing sheet is composed of soft, pliable, natural chamois leather. Intimately laid down on or bonded to this leather is a gritcontaining layer of a suitable thermoplastic binder substance. The grit may be any of those commonly used, such as flint glass, silicon carbide, garnet, emery, aluminum oxide, or the like. It may vary from roughly to 1000 mesh, depending upon the fineness of finish desired. The grits are characterized by various irregular points or edges, defining substantially plane faces or facets, and in the manufacture of the article, these facets are oriented so that the grits tend in large part to lie substantially in a common plane above the outer surface of the binder layer. In general, care is taken to prevent the projection of points or edges of the grits outside this common plane. In use, the plane faces of the grits slide or fioat along on the surface being cleansed or finished, with only the edges of these faces doing work, which is essentially of a scraping or planing nature, rather than of a cutting or digging varity. The chamois leather backing is of a yielding and substantially elastomeric nature, and the individual grits are thus not held with any rigidity against the surface to be polished, but may give instantly upon engagement of any high point thereon to avoid scratching or digging in.

For many applications, the article of the invention is used to most advantage with a slurry of water. For example, the article may be preliminarily immersed in water. Chamois is porous, in that it contains a multiplicity of interconmunicating cells, pores, or interstices between a network of interconnected or interwoven fibers. Thus, the water contacting the surfaces of the chamois penetrates into these cells or pores immediately, and serves as a source of supply during rubbing of the chamois over the work. To facilitate escape of this water or slurry, and to permit it to circulate between the abrasive grits, and thus carry away the detritus removed from the surface undergoing finishing, cleaning, or polishing, the gritbearing binder layer is in the best form of the invention, applied a discontinuous pattern, e.g., in the form of separated elemental areas, such as islands, spot-areas, stripes, or otherwise. The slurry can emerge from the chamois into the spaces or gaps between these elemental areas. islands, stripes, etc., and run off via the channels afforded therebetween. Especially in the case of an oil slurry, the slurry can be applied to the back face of the chamois, as by use of an oil can, and will run through the porous chamois and emerge at the opposite face thereof, particularly within the aforesaid channels. Some of the slurry necessarily covers and flows over and past the islands, and thus carries away the dirt, scum, corrosive substance, adhesive material, or the detritus removed from the surface being finished, and thus unloads the abrasive grit.

Chamois has an elastomeric quality, in addition to softness and pliability, and thus conforms and shapes itself by stretching or deformation to irregular surfaces to be cleaned, after which it returns to its original condition. Similarly, the binder layer in which the grits are embedded is preferably constructed to have an elastomeric characteristic, for similar reasons. It is highly desirable, and a feature of the invention, that the chamois backing and the binding layer have great pliability, and that the pliabilities of the two be substantially equal or compatible, since, otherwise, there is a tendency for the two layers to break from one another and separate. In this connection, a binder layer loaded with grit tends to be quite stiff. By subdividing this grit-bearing layer into small elemental area, such as islands or stripes, the flexibility or pliability of the grit-bearing layer is very greatly improved. This is a readily observable characteristic.

The process by which the article of the invention is produced is susceptible to some variations, but in its present preferred form is as follows:

Abrasive particles of a selected grit size, e.g., 240 mesh, are mixed with a suitable thermoplastic adhesive substance, as for example, a polyvinyl base plastic adhesive commonly sold and known in the trade as heat seal. Incorporated in this mixture is a suitable plasticizer compatible with the adhesive, such as castor oil, or others commonly known. From to (by volume) of a plasticizer for the commercially available polyvinyl heat seal substance is generally satisfactory, but may be adjusted to give a final pliable binder layer as desired. Additionally, a solvent, such as acetone, or methyl ethyl ketone, in the case of polyvinyl, is used to bring the mixture to a consistency suitable for spraying with a conventional spray gun of a type commonly used in the course of the processing of leather hides for coats, pocketbooks, shoes, and gloves, with which those familiar with this art will be fully acquainted. Alternatively, polyurethane in solution, with a suitable hardener, may be used, using solvents such as suggested above.

Some suitable thermoplastic substances available on the market may, as indicated, require a hardener rather than a plasticizer. This is a matter easily handled by those skilled in the art, it only being required that a thermoplastic substance be prepared, mixed with the abrasive particles, and then brought to the proper consistency for uniform spraying from the nozzle of the sprayer at hand, in such manner that a fine, uniform spray is discharged, and can be laid down on the surface of the backing sheet to the desired thickness by making a suitable number of passes over the sheet. The builtup thickness of the applied layer is also not critical, and, at the minimum, need only partially contain the grit. It is simply necessary that this adhesive bind and hold the grit on the surface of the chamois backing sheet. The grits will initially project above the upper surface of the adhesive layer. The adhesive layer is both yielding and elastomeric, and functions as an elastomeric cushion, adhesively bonded to the chamois.

The abrasive thermoplastic coating is then allowed to cure in air for twenty-four hours.

After curing, the leather sheet with the abrasive-bearing thermoplastic layer applied thereto is passed between a system of heated pressure rollers, heated to approximately 170 to 200 degrees F., at which temperature the thermoplastic substance is somewhat softened, and the abrasive particles can be moved or reoriented therein. The spacing between the rollers is small enough that the roller in engagement with the layer of abrasive-bearing thermoplastic coating turns the particles so that their flat sides or faces tend to face upward, and to come into a common plane. The particles in general, of whatever size, are at the same time positioned so as to lie with their uppermost portions either in or below this common plane.

The abrasive-bearing layer of adhesive thermoplastic substance can alternatively be applied to the leather from a roller suitably continuously supplied with the substance, although spraying works very well and is preferred.

To place the abrasive-bearing layer on in separated islands, or stripes, the substance is, in the best form of the invention known to me, sprayed onto the leather through a grid-work or screen positioned close to the leather. I can also apply the abrasive-bearing coating from inside a rotatable drum or roller over which the chamois is caused to travel. In this case, the cylindrical periphery of the drum may comprise a grid-work or screen, and a spray nozzle may be located inside this drum and may spray the adhesive and grit mix from a nozzle inside the drum through the grid-work onto the inside surface of the chamois as it passes over the drum. Alternatively, the applying drum may have raised areas coated with the matrix and abrasive mix, and acts to print the mixture onto the backing layer.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an enlarged sectional view through an abrasive article in accordance with the invention;

FIG. 1a is a view through a portion of the backing layer of the article of FIG. 1 illustrative diagrammatically of its porous character;

FIG. 2 is a very much magnified fragmentary view taken from FIG. 1;

FIG. 3 is a diagrammatic view showing the application of the abrasive-laden matrix to the upper surface of the backing layer;

FIG. 4 is a top plan view of a grid used in FIG. 3.;

FIG. 5 shows the pattern of the abrasive-coated areas resulting from the use of the grid of FIGS, 3 and 4;

FIG. 6 is a diagrammatic view showing the rolling of the abrasive-coated backing layer to accomplish alteration of a large portion of the abrasive particles;

FIG. 7 shoWs diagrammatically an alternative method of applying the abrasive coating layer to the backing layer; and

FIG. 8 indicates diagrammatically another modification.

DESCRIPTION OF A PREFERRED EMBODIMENT In some of the drawings, which are essentially diagrammatic in character, certain proportions have been exaggerated for clarity. True proportions will be appreciated if it is kept in mind that the backing layer is typically of the thickness of chamois leather, and the abrasive particles in the matrix are approximately one layer deep for the larger particles, and these particles may be of the order of 240 mesh, or larger, say of mesh, or down to 800 or even 1000 mesh.

In these drawings, numeral 10 designates an abrasive, polishing article in accordance with the invention, composed of a very soft and pliant chamois leather sheet or pad 11, or equivalent. This sheet, in one important aspect of the invention, must be porous to water or oil, and is characterized by pores, cells or interstices, intercommunieating with one another, whereby water, oil, or any liquid slurry, applied to one surface thereof will immediately run through the leather and appear at the opposite face thereof. Chamois leather is the preferred material, because of its extreme pliability, elastomeric characteristic, softness, smoothness, and porosity. Other substances may in some cases be subtituted, even though lacking all of these qualities. For example, if the article is to be used dry, porosity is unnecessary. And while elastomeric materials are highly preferred, in some cases woven or felted backing sheets, of little or no elastomeric elfect, may be substituted. In general, the range of usable backing materials includes, besides chamois, which is a natural soft leather, synthetic leathers, textiles, and felts. The highly desirable full combination of features and characteristics of chamois, however, when used in my abrasive article, is deemed to be an inventive discovery over substitute or alternative materials.

Coated on the backing sheet 11 is a binder or matrix layer, or coating 12 made up of a thermoplastic substance, as heretofore described, in which has been incorporated or loaded fine abrasive grits 13, of a size, for example, of up to 240 mesh. These grits generally have relatively sharp points and edges, defining relatively fiat faces or facets, and by the process of the invention, the grits are, to the maximum extent feasible, oriented in the adhesive binder layer 12 with the fiat faces or facets 13 of the grits up, or outward, and lying in, so far as can be accomplished, a common plane, as in FIGS. 1 and 2. This plane will be seen to be a short distance above the upper surface of the adhesive elastomeric coating layer 12.

FIG. 3 shows the process of applying'the adhesive coating layer 12 onto the backing sheet 11. On the top of the sheet 11 is positioned a grid 16, which may be a sheet of expanded metal. The nozzle of the spray gun is fragmentarily designated at 16, and is represented as delivering a spray of the liquid or semi-liquid adhesive and abrasive particle mix onto the surface of the sheet 11 between the bars of the grid. These bars should not, preferably, be over about one-eighth inch in thickness, since otherwise the coating operation may be hampered. The coating is built up as heretofore described, preferably by making a succession of passes of the spray nozzle n over the surface to be coated, the nozzle being passed in various directions over the article so as to build up a uniform coating. The thickness of this coating may be two or three mils, but depends of course on the fineness of the grit. FIG. 5 shows the resulting pattern, the abrasive coating having been delivered in diamond shaped areas or islands 30, with continuous channels 31 for flow of slurry therebetween. The ratio of the total area of the islands to the total area of the channels can advantageously be something of the order of four or five to one. In general, a small portion of the adhesive substance may penetrate under the bars of the grid, and be deposited within the channels, where it thins out progressively and then vanishes. This, however, does not occur to a sufficient extent to prevent passage of water through the channel areas 31 of the backing sheet, between islands 30. Thus, water or other liquid slurry sprinkled on the reverse side (lower side in FIG. 5) of the article but generally upper side in usage on upwardly facing work, will emerge immediately in the channel areas, and will run therealong, carrying away detritus, as earlier eX- plained. The slurry also protects the coating layer from cracking, and has the additional function of carrying off loosened material which otherwise often tends to load the abrasive, and mask or stop its intended action.

The article, after spraying on of the coating 12, is allowed to cure in air for twenty-four hours, and is then passed between two heated rotatable pressure rollers 34 (see FIG. 6) spaced apart sufiiciently to smooth out any raised areas of the sprayed-on coating, and to engage and orient the abrasive particles, as heretofore described, so that their plane faces largely or predominantly conform substantially to a common plane. The heated rollers soften the thermoplastic substance sufficiently to accommodate this reorientation.

The layer of thermoplastic abrasive-bearing material 12 can also be applied, and in an island pattern, by a drum 40 (FIG. 7) having a foraminous cylinder 41 rolling against the backing sheet passing against it. The pattern of the foraminous cylinder may again be diamond shaped, if desired, or otherwise. A spray nozzle n delivers the mix of adhesive, thermoplastic substance through the openings of the foraminous cylinder onto the surface of the backing sheet 11.

Still another method of application involves the use of a roller such as 40 (FIG. 8), provided with raised islands or lands 41' on its periphery, and adapted to have the backing layer 11 drawn thereacross. The mix of thermoplastic material and abrasive particles is applied to or coated on the roller 40 from a transfer roller 42 which peripherally contacts the roller 40', and to be supplied with the mix in any conventional fashion. The coated lands on the roller 40 are, in effect, printed onto the backing sheet 11.

One of the principal virtues and accomplishments of the present invention resides in the use of novel backing elements affording a very much improved cushion for the abrasive particles. It will be recalled that it is partly owing to the common orientation of the fiat faces of the particles into a working plane, and partly to the cushioned support for these particles, that the particles yield so readily when they encounter the work surface, and thus avoid any real cutting abrasion thereof. An unusual characteristic of the article of the invention is that, when in use, the heat of friction can slightly soften the thermoplastic layer bonding the abrasive particles, and thus the particles can rock or oscillate slightly during work to accommodate their flat working surfaces to the surface being polished. The soft backing sheet, together with the softness of the thermoplastic binding layer while in use, are jointly responsible for this novel and useful performance. A further unique feature of advantage of the article of the invention is that the backing layer (preferably chamois) is not only relatively soft and pliable as well as elastomeric, but that the backing layer and the abrasive-bearing layerhave similar pliabilities, so that they flex together, and there is an absence of material separate stress. The final feature desired to be emphasized at this point is the capacity for free circulation of liquid slurry through the chamois or equivalent backing sheet, in between the abrasive particles, and outward by way of the channels between islands.

Ideally, virtually all the abrasive particles would be oriented with fiat facets thereof in the common work plane. However, many of the particles are too small for such orientation, and the meaning is then that the objective is to so orient a preponderance of those particles large enough that orientation can be accomplished. Again, however, the cushion provided by the present invention is so soft and yielding that desirable results for many applications are accomplished irrespective of the degree of orientation achieved.

I claim:

1. A polishing article comprising:

a porous backing pad adapted to fill with liquid slurry,

a yieldable layer of thermoplastic binding substance in an overall discontinuous pattern on one face of said pad, so as to afford within and throughout said pattern uncoated gaps through which liquid slurry within the porous pad can emerge, and

a multiplicity of abrasive grits embedded in said binding layer and yieldably supported in said layer on said porous pad, said grits being exposed to the work at the side of said binding layer opposite from said pad, with a substantial proportion of said grits having relatively flat facets oriented to lie substantially in a common plane adjacent said side of said binding layer.

2. The article of claim 1 where said gaps in said bind ing layer are in the form of elongated flow channels into which liquid slurry delivered to the opposite face of the porous pad can emerge.

3. The subject matter of claim 1 wherein said backing pad has substantially the elastomeric, pliability and porosity characteristics of chamois leather.

4. The subject matter of claim 1 wherein said backing pad is composed of a chamois-like substance.

5. The subject matter of claim 1 wherein said backing pad is soft, pliable, and yieldingly deformable.

6. A polishing article comprising:

a backing pad having substantially the elastomeric,

pliability, softness and porosity characteristics of chamois leather,

a pliable binding layer of a yieldable thermoplastic binding substance on one face of said pad, and

a multiplicity of abrasive grits embedded in said binding layer and yieldingly supported in said layer on said backing pad, said grits being exposed to the work at the side of said binding layer opposite from 7 8 said pad, with a substantial portion of said grits hava multiplicity of abrasive grits embedded in said binding relatively fiat facets oriented to lie substantially ing layer and yieldably supported in said layer on in a common plane adjacent said side of said binding said porous pad, said grits being exposed to the work layer. at the side of said binding layer opposite from said 7. A polishing article comprising: pad.

a backing pad of chamois leather, 9. The polishing article of claim '8, in which the porous a pliable binding layer of a yieldable thermoplastic backing pad is soft and pliable.

binding substance on one face of said pad, and

a multiplicity of abrasive grits embedded in said bind- References Cited ing layer and yieldingly supported in said layer on 10 UNITED STATES PATENTS sa1d backing pad, sa1d grits belng exposed to the work at the side of said binding layer opposite from 1,988,065 1/1935 Wooddeu 51-293X said pad, with a substantial portion of said grits 2,015,658 10/1935 Bezzenbel'ger 51' 293X having relatively flat facets oriented to lie substan- 2,188,341 1/1940 El'bel et tially in a common plane adjacent said side of said 746505158 8/1953 Eastman 51-407X binding layer. 2,665,528 1/1954 Sternfield et a1. 51-402X 3,230,672 1/1966 Anthon 51404 8. A polishing article comprising:

a porous backing pad adapted to fill with liquid slurry,

a yieldable layer of thermoplastic binding substance in an overall discontinuous pattern on one face of said pad, so as to afford within and throughout said pattern uncoated gaps through which liquid slurry 7 within the porous pad can emerge, and

GRANVILLE Y. CUSTER, JR., Primary Examiner US. Cl. X.R. 

